A gas turbine engine may be used to supply power to various types of vehicles and systems. For example, gas turbine engines may be used to supply propulsion power to an aircraft. Many gas turbine engines include at an intake section, a compressor section, a combustor section, and a turbine section. The intake section includes a fan, which draws air into the engine and accelerates it. A fraction of the accelerated air exhausted from the fan is directed through an engine bypass section disposed between a fan case and an engine cowl, and provides a forward thrust.
The compressor section, which may include two or more compressor stages, receives the flow of intake air from the fan and raises the pressure of this air to a relatively high level. The compressed air from the compressor section then enters the combustor section, where a ring of fuel nozzles injects a steady stream of fuel. The injected fuel is ignited by a burner, which significantly increases the energy of the compressed air.
The high-energy compressed air from the combustor section then flows into and through the turbine section, causing rotationally mounted turbine blades to rotate and generate energy. The air exiting the turbine section is then exhausted from the engine. Similar to the compressor section, in a multi-spool engine the turbine section may include a plurality of turbine stages. The energy generated in each of the turbines may be used to power other portions of the engine.
In addition to providing propulsion power, a gas turbine engine may also, or instead, be used to supply either, or both, electrical and pneumatic power to the aircraft. For example, some gas turbine engines include a bleed air port on the compressor section. The bleed air port allows some of the compressed air from the compressor section to be diverted away from the combustor and turbine sections, and supplied to various pneumatic loads. These pneumatic loads may vary, but may include air conditioning, bay ventilation, and cabin pressure control, just to name a few.
No matter the specific pneumatic loads, before the engine bleed air is supplied to these loads, it is typically cooled to a lower, more acceptable temperature. In turbofan gas turbine engines, bypass fan air may be controllably supplied to a heat exchanger. In the heat exchanger, heat from the engine bleed air is transferred to the cooler bypass fan air. The flow of the bypass fan air, and thus the temperature of the engine bleed air exiting the heat exchanger, may be controlled by a fan air valve (FAV). In particular, an FAV controller supplies valve position signals to the FAV to control its position, and thus engine bleed air temperature.
Many presently known FAV controllers use position feedback to provide suitable response requirements. However, ambient temperatures in some engine nacelles may be too high for a suitable position feedback device. Moreover, existing classical control methods on temperature may not exhibit desirable transient responses.
Accordingly, it is desirable to provide a control system and method for a FAV that provides a suitable response time and/or does not exhibit undesirable overshoot and/or uses sensors that may be used in other control functions of various engine nacelles. The present invention addresses at least these needs.